This invention relates to a welding apparatus for gas-shielded arc welding operations. This invention relates in particular to welding guns for such welding operations which effectively remove fumes from the vicinity of the arc-welding zone, yet at the same time is convenient to use.
Arc-welding operations are known to produce undesirable fumes during the welding process, many of them,such as certain oxides of nitrogen or carbon, being particularly noxious to the welder or others in the vicinity of the welding operation. Such fumes when allowed to accumulate in confined spaces have long been known to constitute a safety hazard, as well as an interference to welder visibility and general welding operation efficiency, and numerous means have been employed by the welding industry to dissipate these fumes as they are generated.
Measures have been taken to provide generally adequate air ventilation in the welding area, where possible; however, this is frequently not possible when for example the welding operation must be accomplished in a confined space. Additionally, suction fans in cooperation with adjustable flexible tubes containing a hooded open end or duct have been used near the welding zone for fume exhaustion: these exhaust means have the disadvantages of requiring relocation of the duct as the arc welding zone changes, and, further, of interfering with the flow of shielding gas to the welding zone in the event of improper adjustment of the vacuum or improper placement of the duct.
More typically, these fume exhaust and ventilation means have been supplemented or replaced by fume extraction devices generally comprising a conduit associated with the welding gun through which undesirable product gases of the welding operation are extracted by means of a vacuum applied to the conduit. Examplary of such welding guns are those disclosed in French Pat. No. 1,526,305; U.S. Pat. No. 3,514,567; and U.S. application Ser. No. 354,193, of common assignment herewith. These guns broadly comprise dual conduit welding guns wherein one conduit contains the conventional components of the welding apparatus, and the other conduit provides a passageway for extraction of undesirable fumes. It is further customary in the welding industry to provide known welding guns such as disclosed in U.S. Pat. No. 3,629,547 with fume extraction tubes, typically disposing these tubes alongside or immediately adjacent to the welding gun; the gun and extraction tube again thereby comprise a dual conduit structure.
These dual conduit welding gun structures are frequently cumbersome, constituting a heavy structure frequently having a relatively unwieldy cross-section, particularly adjacent the control handle and flexible connector portions of the gun.
Often, the welding wire and associated electrically conducting elements are disposed relatively proximately to the external case, resulting in relatively hot handle and connector portions of the welding gun during operation, which frequently necessitates lowering of current levels to the welding gun, thereby decreasing weld rate or speed of weld metal deposition.
Still further, many prior art welding guns are provided with multiple tubes, conduits, cables, and the like, which are formed into bundles and attached to the external surface of the welding gun. These bundles frequently constitute substantial projections, which are susceptible to being snagged, these interfering with the maneuverability of the apparatus.